Ambient condition detection systems, such as fire alarm systems, often provide a separate loop for audible/visible output devices. In these devices, horns and/or strobes can be driven to emit alarm indicating outputs as appropriate. One exemplary form of audible/visible output device has been disclosed in U.S. patent application Ser. No. 10/040,968 filed Jan. 2, 2002 for Processor Based Strobe with Feedback assigned to the assignee hereof and incorporated by reference herein.
Normally this loop is not energized. It might have a non-operational (reversed) voltage applied thereto during non-alarm intervals for supervision purposes. To activate the devices the polarity of the loop voltage is reversed from for example, minus 5 volts to plus 24 volts. As is well known, all the devices on the loop will then emit audible and/or visible alarm indicating outputs. Having all the devices on the loop active at once, as described below can at times be undesirable.
Such devices are often respectively controlled or synchronized by a periodic control pulse or pulses embedded in the driving voltage. Such systems have been disclosed and claimed in U.S. Pat. No. 5,598,139 for Fire Detecting System with Synchronized Strobe Lights and U.S. Pat. No. 5,850,178 for Alarm System Having Synchronizing Pulse Generator and Synchronizing Pulse Missing Detector assigned to the assignee hereof and incorporated by reference herein.
Pulse width modulation or pulse position modulation can be combined with such pulse sequences to provide additional control functions all without limitation. The synchronizing or controlling pulse trains or sequences are usually responded to by all of the devices on the loop for the duration of time during which the pulses are present on the loop.
It has also been recognized that there is virtue in modularizing such systems and making it easy to install and/or replace electrical units including ambient condition detectors, output devices and the like all without limitation. Hence, such electrical units are often equipped with quick connect/disconnect-type contacts whereby one portion of the contact is permanently installed in a part of the system, and, the other portion of the contact is carried by the electrical unit. When the two parts of the contact mate, the connection is completed and the electrical unit can be expected to perform as expected.
It is also known that it is desirable to be able to test such electrical units at the time of installation and/or on a periodic basis thereafter. Testing can take place by energizing the electrical units in a normal operational fashion and detecting, either automatically or manually, the response of the electrical unit or units thereto. Hence, where the electrical units correspond to output devices, once several of them have been newly installed in the system, all of the output devices on that particular loop can be driven and the operationality of the newly installed units, as well as all of the preexisting units can be verified. This however, is inconvenient in that it produces nuisance alarm conditions, since all the units are active which is undesirable.
There is a continuing need to be able to verify operationality of newly installed electrical units, be they detectors or output devices, without creating nuisance alarms. Preferably, such indications could be generated conveniently during the installation cycle, substantially immediately when the electrical unit is installed to provide feedback to the installer in real time. Preferably, such feedback capability could be incorporated into electrical units being newly installed in existing systems, as well as those being installed in new systems, without causing substantial additional manufacturing or installation costs in both existing and new systems.